NASA has gone from rocketing astronauts to the moon to hurtling the first spacecraft ever to reach the interstellar space. The phrase, “sky is the limit” miserably fails when applied to NASA; but there was still one stunt that the seemingly all-powerful NASA couldn’t pull off – sending a probe to the sun.
The sole and obvious deterrent was our nearest star’s searing heat, whose surface burns at 10,000°F, and it’s outer atmosphere—the corona— goes as high as 3.5 million degrees Fahrenheit.
This video has more explanation
But recently NASA has announced that their probe will make it to the surface of the sun. How is this possible? What materials and cooling techniques will NASA employ?
NASA came up with a special heat shield constructed using carbon-carbon composite, which helps keep the probe’s instruments and electronics within the 70-degree range even when the probe is within touching distance of the star.
Since space is a complete vacuum, the heat will only be transferred via radiation. Some parts of the probe will reach 1500 K but not the entire contraption. Electronics will be guarded by an insulated reflector casting a cool shadow and reflecting the sunlight away.
Shield radiators fixed behind the reflector will radiate away the heat into the vacuum, with a heat pump flowing a fluid with a boiling point of 300 K behind the solar panels. This fluid runs through a compressor, which compresses it 5 times its original volume and raises the temperature to 1500K. The fluid is then passed through the radiator that throws out the heat into space.
You might ask why raise the temperature of the cooling fluid in the first place? This is because radiative heat transfer is proportional to the fourth power of absolute temperature, or more precisely,
So a fluid at 1500K will radiate 625x more Watts per sq meter than 300K fluid, 459.3 W/m2 vs. 287,043.7 W/m2 to be precise.
Rounding things off would be the high-efficiency solar panels that operate at high temperatures and reflect away ineffective light.
Damn these astrophysicists are creative!